The Samsung CLP-320 printer's static ip 192.168.1.139 was set about
10 years ago to work on a lan using 192.168.1.x addresses. Last week
the lan's router failed and was replaced with a Netgear r6700 router
using 192.168.2.x addresses. The printer is now inaccessible from the
lan.

Cups Administration says the printer address can be set using its MAC
address:

Configuring the IP Address Using DHCP

The DHCP protocol is the usual way of setting the IP address of a
printer on a managed network. Using the standard dhcpd(8) program
supplied with UNIX you simply need to add a line to the
/etc/dhcpd.conf file: